Problem: $\dfrac{7}{4} - \dfrac{7}{5} = {?}$
Explanation: $ = {\dfrac{7 \times 5}{4 \times 5}} - {\dfrac{7 \times 4}{5 \times 4}} $ $ = {\dfrac{35}{20}} - {\dfrac{28}{20}} $ $ = \dfrac{{35} - {28}}{20} $ $ = \dfrac{7}{20}$